public class Test {
    public static void main1(String[] args) {
        String s = "hello";
        // 字符串转数组
        char[] ch = s.toCharArray();
        for (int i = 0; i < ch.length; i++) {
            System.out.print(ch[i]);
        }
    }
    public static void main6(String[] args) {
        String s = "AbCdEf";
        System.out.println(s.toLowerCase());
        System.out.println(s.toUpperCase());
    }
    public static void main5(String[] args) {
        Integer a = Integer.parseInt("123");
        Double b = Double.parseDouble("123");
        System.out.println(a);
        System.out.println(b);
    }
    public static void main4(String[] args) {

        String str = "abcdefg";
        int ret = str.indexOf('b');
        System.out.println(ret);
        char ch = str.charAt(1);
        System.out.println(ch);
    }
    public static void main3(String[] args) {
        String str1 = new String("1234");
        String str2 = new String("1234");
        int ans = str2.compareTo(str1);
        System.out.println(ans);
    }

    public static void main(String[] args) {
        String str1 = new String("1234");
        String str2 = new String("1234");
        System.out.println(str2 == str1);
    }
    public static void main7(String[] args) {
        String str = new String("abcdef");

        String str1 = "abcdef";

        char[] ch = {'a','b','c'};
        String str2 = new String(ch);
    }
}
